In commercial equipment for producing confectionery frozen foods such as ice cream and frozen yogurt, the recipe materials for the desired frozen food are introduced into a cylindrical chamber and then thoroughly mixed to provide a uniform consistent edible, usually creamy mass. The mixing is accomplished by a longitudinal mixer rotor commonly called a beater installed in the cylinder, such mixer rotor having a single longitudinal helical beating or mixing blade extending in helical relation about the axis of rotation of the empty outer periphery of the beater. In addition to the helical blade, the beater has straight longitudinal metal scraper blades having a length about half the length of the mixing rotor itself, usually two in number supported at diametrically opposite sides of the rotary mixer and at opposite ends of the rotor. The blades extend parallel to the rotor axis of rotation with their sharp scraping edge moveable to the radially outer-most position where they can make contact with material accumulated on the interior wall of the longitudinal cylinder thereby causing them to effectively remove frozen material from the interior wall of the freezer surface as the beater is rotated.
To effect the scraping or wiping of the cylinder wall by the scraper blades, they are each pivotally supported upon a pair of spaced mounting pins or prongs projecting from the rotor in a direction generally away from the rotor axis of rotation for extension through mounting apertures provided at opposite ends of the blade. The support prongs are slightly arced and the apertures are large enough such that the blades are loosely mounted thereon to permit them to move about their back edge with an arced movement radially outwardly under centrifugal force as the mixer is rotated, whereupon the blades extend themselves to their outermost reach as permitted by the dimensions of the interior surface of the cylindrical chamber.
In other words the scraper blades are each mounted so that their scraper edge is moveable laterally inward to a degree such as to provide clearance for easy installation of the rotor within the cylinder. The scraper edge is moveable outwardly from its inward position under the influence of centrifical force and by the push on the blade by material being mixed. The scraper edge thus moves toward the interior surface of the cylinder to effect removal of the frozen material coated thereon.
A significant problem confronted in conventional equipment of this type is that the blades of metal, usually of surgical stainless steel, frequently make direct contact with the metallic interior surface of the cylinder while scraping the material therefrom. This results in a wearing away of both the interior metallic surface of the freezer and the thin sharp edge of the metallic scraper blade. With such wear, particles of metal become mixed into the frozen food produced by the freezer. Although visually imperceptible, the particles are undesirably present as metallic contaminants in the foods produced by such equipment for consumption.
Additionally as surfaces of both the blade and the freezer interior wear away, the wear is frequently nonuniform thus preventing uniform and complete scraping of the frozen material from the chamber sides. Scoring of the interior surface thus at times results necessitating costly repairs to bring the freezer up to at least norm in operation according to design specifications.
In view of the foregoing difficulties, it is an object of the invention to reduce or eliminate the presence of metal particles in the frozen confectionery product produced by such machines by eliminating metal to metal contact between the scraper blades and the interior wall of the freezer chamber.
It is another object of the invention to provide a mixer scraper blade shaped such that the usual tendencies toward buildup of material on the blade itself are minimized which operates quietly with reduced tendency to score the metallic interior surface of the freezer cylinder and at the same time being more effective in scraping frozen material from the chamber sides.
Still further it is another object of the invention to provide a scraper blade of resinous material having a longer operational life than conventional metal blades and also being of material which will minimize bacterial growth by reason of the greater ease of cleaning such blades.